Combined biochemical, genetic and morphological procedures will be employed to examine the following: regulation of the synthesis of a specific protein and DNA, mechanisms of uncoating and the modification of cell membranes that are induced or modulated by virus infection. Concerning the poxviruses (1) temperature-sensitive mutants of vaccinia may reveal whether enzymes contained within inoculum particles participate directly in DNA synthesis. (2) Large crystalloids rich in vaccinia DNA will be allowed to form under specified inhibitory conditions, then will be purified and analyzed for their content of protein to ascertain whether in this group basic proteins play a role in repression of synthesis and transcription of the virus genome. (3) The cytoplasmic "A" bodies induced by cowpox, containing a distinctive protein mass appear to be organized so as to function as discrete "organelles" for synthesizing protein in situ. The specificity of the mRNA involved and regulation of its translation will be analyzed. (4) Control of fusion and intercellular spread of infection will be examined in vitro as a microepidemiological model of poxvirus infections in man and animals. Specifically the influence of mutants that induce polykaryocytosis and those that do not will be considered in relation to cell membrane interactions. Previous studies on penetration and intracellular release of genomes from the inoculum will be continued. As one model for nucleo- cytoplasmic transfer the release of DNA from adenoviruses at the nuclear envelopes will be followed. From these studies we may be able to determine whether cellular ATPase in the "nuclear pore complex" is involved in the uncoating of this virus group.